1. Field of the Invention
The present invention is generally related to an integrated hydraulic steering actuator and, more particularly, to an actuator for an outboard motor that comprises a hydraulic cylinder that is located within a generally cylindrical portion of a swivel bracket attached to the outboard motor and rotatable relative to a clamp bracket that is attached to a boat.
2. Description of the Prior Art
Many different types of steering actuators are well known to those skilled in the art of marine propulsion systems. Steering can be accomplished with a mechanical system comprising cables that are attached between a steering wheel and an outboard motor. Hydraulic steering systems generally utilize a hydraulic pump that is actuated by a steering wheel and connected in fluid communication with a hydraulic cylinder attached to the outboard motor. Power steering systems generally use a pump that is actuated in response to movement of a steering wheel, wherein the pump is associated with appropriate valving to provide pressurized hydraulic fluid to a hydraulic cylinder attached to the outboard motor.
U.S. Pat. No. 5,997,370, which issued to Fetchko et al on Dec. 7, 1999, describes an outboard hydraulic steering assembly with reduced support bracket rotation. The assembly supplies a force to a tiller arm of a marine outboard propulsion unit and rotates the propulsion about a steering axis between a center position and hard over positions to each side of the center position. The propulsion unit is supported for arcuate movement about a tilt axis which is generally perpendicular to the steering axis. The steering assembly includes a hydraulic steering cylinder with an elongated piston rod reciprocatingly mounted within the cylinder for movement along a piston rod axis. A pair of support arms are pivotable about the tilt axis and are connected to the piston rod, allowing arcuate movement of the rod about the tilt axis, while maintaining the rod axis parallel to the tilt axis. A member is pivotally mounted on the tiller arm for pivoting about a first axis which is parallel to the steering axis. The cylinder arm is connected to the cylinder and extends radially outwards from the piston rod axis. The cylinder arm is pivotally connected to the member for pivoting about the second link axis which is parallel to the piston rod axis. The cylinder arm moves through a partially rotated position when the propulsion unit rotates from the center position to either hard over position. The second link axis and the rod axes are on a plane parallel to the steering axis at the partially rotated position.
U.S. Pat. No. 5,092,801, which issued to McBeth on Mar. 3, 1992, describes a hydraulic steering assembly for outboard marine engines. The assembly is connected to the tiller arm of an outboard marine engine and includes a piston rod supported for arcuate movement about the tilt axis while remaining parallel thereto. A hydraulic cylinder travels along the piston rod. An arm extends from the cylinder to a first pivotal member establishing a first pivotal connection about an axis parallel to the tilt axis. A rigid link extends between the first pivotal member and a second pivotal member. The second pivotal member is also connected to the tiller arm and establishes a second pivotal connection about an axis perpendicular to the tilt axis. As the cylinder travels back and forth across the rod, the piston rod oscillates about the tilt axis, the cylinder rotates about the piston rod, the arm rotates about the first pivotal member and the link rotates about the tiller arm in a concerted motion providing a strong and compact linkage arrangement.
U.S. Pat. No. 5,330,375, which issued to Tsujii et al on Jul. 19, 1994, describes a steering system for a marine propulsion unit. The mechanism for a marine outboard drive is disclosed wherein the steering rod connected to the outboard drive end of the wire actuator steering cable is slidably mounted in a guide tube that is formed integrally with the hydraulic assist cylinder and which are affixed to the transom independently of the tilt pin and forwardly of it. This permits the steering mechanism to be assembled as a unit separately from the outboard drive and attached to the transom separately from it.
U.S. Pat. No. 5,542,864, which issued to Peebles on Aug. 6, 1996, describes a steering cylinder for an outboard engine. The cylinder has an elongate interior chamber, a piston movable in the chamber, and a first fluid passage generally parallel to the chamber. In the improvement, the cylinder includes a second fluid passage generally parallel to the chamber and both passages terminate at faces at either end of the cylinder housing. Air bleed fittings and hydraulic fluid fittings are at the faces and, because of such location, jammed and broken fittings and damage to the boat transom and other structure are substantially avoided. Since each passage has both bleed and fluid fittings, it is not necessary to open a fluid fitting to bleed the cylinder during installation.
U.S. Pat. No. 4,710,141, which issued to Ferguson on Dec. 1, 1987, describes a marine propulsion device power steering system. The device includes a propulsion unit mounted for tilting movement about a generally horizontal tilt axis and for pivotal steering movement about a vertical steering axis, and a power steering system adapted to operably connect an actuator to the propulsion system for increasing the steering force applied to the propulsion unit by the actuator. The power steering system is wholly supported on the propulsion unit and includes a hydraulic cylinder-piston assembly having an axis extending in fixed parallel rotation to the tilt axis and including a cylinder, a piston mounted in the cylinder, and an extendable and retractable piston rod connected to the piston rod and a control valve connected to a source of pressurized hydraulic fluid for selectively controlling the flow of hydraulic fluid to and from the opposite sides of the piston to extend and retract the piston rod. The control valve includes a valve member and valve housing rotatably and axially movable relative to each other. The valve member is connected to the actuator and the valve housing is connected to the piston rod for common movement and is connected to the propulsion unit to affect steering movement thereof in response to movement of the actuator.
U.S. Pat. No. 5,924,379, which issued to Masini et al on Jul. 20, 1999, discloses an actuating mechanism with an improved mounting structure. The mechanism is provided with support members that extend away from the centerline of a cylinder bore, piston and actuator rod of an actuation mechanism that uses pressure to move the piston within the cylinder bore. Two support members are attached to a cylinder housing and provided with mounting holes. The two support members are spaced apart from the cylinder housing to allow external support structures to be placed between the cylinder housing and the two support members. Appropriate fasteners, such as bolts, attach each of the two support members to the external support structures in such a way that the cylinder housing can pivot about an axis extending through both bolts. Most importantly, the line extending through the support bolts intersects the cylinder bore at a place between its opposing ends. This reduces the required space necessary to allow the cylinder to pivot properly.
U.S. Pat. No. 5,002,510, which issued to Rump on Mar. 26, 1991, describes a steering mechanism for a marine propulsion device. The invention provides a hydraulic steering assembly for a marine propulsion unit in which the axis of the cylinder travels parallel to the axis of the propulsion unit tilt axis during pivotal steering of the propulsion unit. The steering assembly provides two, two-bar link arms interconnecting the tilt tube and cylinder rod.
U.S. Pat. No. 4,632,049, which issued to Hall et al on Dec. 30, 1986, describes a marine propulsion steering assist device. The device comprises a propulsion unit pivotable about a first steering axis to steer a marine vehicle, a trim tab mounted on the propulsion unit and pivotable about a second steering axis for assisting and steering the vehicle, and a hydraulic sensing arrangement for sensing torque on the propulsion unit relative to the first steering axis to pivot the trim tab in response to the torque. The device also includes steering mechanism for pivoting the propulsion unit about the first steering axis to steer the vehicle. The steering mechanism includes a steering member connected to the propulsion unit, and operable to move the steering member to pivot the propulsion unit. The steering mechanism is operable to move the steering member and includes a push-pull cable with a core and a flexible housing. The hydraulic sensing arrangement permits lost motion between the flexible housing and the steering member and the hydraulic sensing arrangement senses torque on the propulsion unit relative to the first steering axis by movement of the flexible housing relative to the steering member.
U.S. Pat. No. 4,615,290, which issued to Hall on Oct. 7, 1986, describes a marine propulsion steering assist device. The device comprises a propulsion unit pivotable about a first steering axis to steer a marine vehicle, a trim tab mounted on the propulsion unit and pivotable about a second steering axis for assisting in steering the vehicle, and a hydraulic sensing arrangement for sensing torque on the propulsion unit relative to the first steering axis to pivot the trim tab in response to the torque.
U.S. Pat. No. 5,244,426, which issued to Miyashita et al on Sep. 14, 1993, describes a power steering system for an outboard motor. A power steering system for an outboard motor for steering an outboard motor disposed outside of a rear portion of a hull and usually including a manual steering system mounted upon the hull for operating a steering element so as to manually steer the outboard motor body, is disclosed. A power unit is operatively connected to the manual steering system and includes an electric motor for applying a steering assist force to the manual steering system. The power unit is located at the portion of the hull capable of effectively utilizing the inner space of the hull and the electric motor of the power unit is controlled by means of a control unit in accordance with the navigation conditions of the hull and the operating conditions of the outboard motor as detected by means of suitable sensors. The sensors comprise various sensors such as, for example, a steering torque sensor and an engine speed sensor.
The patents described above are hereby explicitly incorporated by reference in the description of the present invention.
Several types of steering cylinders are available from Teleflex Inc. and are commercially available under the Seastar brand. These include a front mount cylinder identified as part number HC5345, a side mount cylinder identified as part number HC5370, and a splashwell mount cylinder identified as part number HC5380. In addition, a steering cylinder is available from the Hynautic Company which is attachable to an existing outboard motor propulsion system.
Steering actuators known to those skilled in the art are typically provided as after-market devices that can be attached to an existing outboard motor. As such, these after-market devices typically exhibit several disadvantages. Many types of steering actuators are placed at a location that is offset from the actual tilt axis of the outboard motor. As a result, tilting the outboard motor causes the actuator to move relative to the transom of a boat and along a path that can interfere with other components. In order to avoid this disadvantage, some after-market steering actuators are placed either to port or starboard from the outboard motor and aligned with the tilt axis of the outboard motor. Although this technique avoids the relative movement of the actuator to the transom when the outboard motor is tilted, it requires additional space for the actuator, either to the port or starboard of the outboard motor.
It would therefore be significantly beneficial if a steering actuator could be located relative to the outboard motor in a position that does not require the actuator to move along a path relative to the transom of the boat as the outboard motor is tilted and, furthermore, it would be beneficial if the steering actuator could be conveniently located in a position that does not require additional space for the actuator components.